Effects of moulding pressure and w/c induced pore water saturation on the CO2 curing efficiency of dry-mix cement blocks

Abstract

CO2 curing, also known as accelerated carbonation is considered as a promising technique to mineralize CO2 and enhance the properties of cement-based materials. Since the amount of pore water saturation can control the carbonation rate, this paper aims to investigate the optimal moulding pressure (MP of 10, 15 and 20 MPa) and water-to-cement ratios (w/c of 0.125, 0.15 and 0.175) that could maximize the carbonation reaction as well as the properties of 2 h CO2 cured dry-mix cement blocks. The results found that increasing the pore water saturation from 50.6% to 91.9% by changing w/c and MP, inhibits the CO2 diffusion from surface to the innermost layer. The carbonation depth was also reduced from 7 mm to nearly 0 mm for the respective cement blocks. The change of pH value along the carbonation depth could indicate the CO2 diffusion pathway. The CO2 uptake result was corroborated with this finding too. However, it is found that MP is more dominant in determining the pore saturation whereas w/c is more dominant in controlling the strength development and carbonation depth. The optimal values of w/c and MP are 0.125 and 20 MPa respectively, which resulted in the highest compressive strength of 56 MPa upon 2 h of CO2 curing.